I'm in a similar position to you. I just finished Year 11 and did C1, C2, C3 + M1 in June. My module scores were 100 in C1, 88 in M1 (getting remarked, predicted 97-100), 89 in C2, 92 in C3. I too want to know if you can do resits and still get into Cambridge. The kind of mistakes I made were stupid ones, like not adding properly for a definite integration, or for solving 210 = 220x, doing 220/210 instead of 210/220. Will be keeping an eye on this thread.